The invention relates generally to semiconductor device and integrated circuit fabrication and, in particular, to fabrication methods, device structures, and design structures for a bipolar junction transistor.
Bipolar junction transistors may be utilized in integrated circuits designed for high-frequency applications and in integrated circuits designed for high-power applications such as power amplifiers. Generally, a bipolar junction transistor is comprised of three distinct semiconductor regions that define terminals, namely an emitter, a collector, and a base disposed between the emitter and collector. An NPN bipolar junction transistor includes a layer of p-type semiconductor material constituting the base and two layers of n-type semiconductor material constituting the emitter and collector. The layers of n-type semiconductor material are sandwiched between the two layers of n-type semiconductor material. The conductivity types of the semiconductor materials for the emitter, base and collector in a PNP bipolar junction transistor are reversed. Generally, the differing conductivity types of the emitter, base, and collector form a pair of p-n junctions, namely a collector-base junction and an emitter-base junction. A voltage applied across the emitter-base junction controls the movement of charge carriers between the collector and emitter.
Improved fabrication methods, device structures, and design structures are needed for a bipolar junction transistor.